Exploring the temperature rise under low-energy electron irradiation for various materials

Abstract

Scanning electron microscope (SEM) is frequently-used in analysis for micro/nanoscale structural information. During SEM analysis, besides the widely-known charging effect, the temperature rise because of electron beam bombardment has become an issue due to it also can modify SEM results with the downsizing of specimen. In this work, a sophisticated Monte Carlo (MC) model which considered the cascade electron production was adopted to quantitatively study the temperature rise during SEM imaging. The rule of temperature profile was explored focusing on four different materials (semi-infinite beryllium (Be), magnesium (Mg), copper (Cu) and gold (Au) bulks) and primary electron (PE) beam energies. It was concluded that the temperature profile presents three main characteristics: a) increasing first at surface until its maximum is reached, then has a sharp reduction as a function of depth from the surface for all materials; b) being affected seriously by PE energy and atomic number. The temperature rise integral from high to low is Be > Cu > Au > Mg; c) various elements show different capabilities of heat transfer direction and speed. The mechanism behind these observations was explained in detail. In addition, the temperature rise was investigated briefly on two overlayer structures (Be/Au and Au/Be), showing discontinuous jumping at the interface for two types of materials. This work on the one hand, provides a better understanding and elucidation for physical mechanism of electron-beam-induced deposition, of which process control, performance and reliability would thus get greater improved based on this study, on the other hand, reveals a potential implication that some damages caused by the heat transfer under electron irradiation in a SEM operation might be effectively avoided or reduced through selecting appropriate materials according to their different heat transfer performances.